Having sturdy jaws is essential for the small marine creatures known as bloodworms.
The worms, which grow to about 15 inches in length, spend their lives burrowing through the muddy seafloor and hunting small crustaceans, molluscs, and other worms.
“They need their jaws to kill the more active prey,” says Herbert Waite, a marine biochemist at the University of California, Santa Barbara. “They also use the jaws to fight each other off because they’re not very sociable, and occasionally the worms will collide in the burrows.”
The jaws must be both very sharp and very tough because bloodworms only make them once during their lifetimes, Waite says. The key to this fearsome maw lies in a unique mix of copper, melanin, and a protein with some impressive chemical properties, he and his collaborators reported on April 25 in the journal Matter. The worms’ efficient jaw-building process may hold insights for improving how composite materials—which are made from a mix of different substances—are manufactured, the team concluded.
Each bloodworm sports a proboscis with four black jaws to grasp other animals and inject them with paralyzing venom. These hollow fangs are lightweight but can withstand a lot of wear and tear thanks to their melanin and copper components, Waite and his colleagues wrote in the new paper. These are unusual ingredients for animal jaws. Copper is “usually quite toxic” to animals, Waite says, and melanin is a pigment that rarely serves as a structural element.
“We’ve had an interest in how different marine invertebrates make load-bearing structures for survival, and this one stood out in particular because it was one of the only ones reported to have high copper content,” he says.
Scientists aren’t sure why the worms opted for copper rather than another metal more typically used by marine invertebrates, such as iron or zinc. However, one possibility is that the copper reacts with the venom stored in the fangs. “The worm has the luxury of storing these toxins in some kind of less harmful or inert form and they become toxic as they move through the channels in the jaw on their way into the prey,” Waite says.
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To investigate how bloodworms put their distinctive fangs together, Waite and his team identified the genetic sequence that codes for the main protein in the jaws. They found that the protein’s chemical composition was fairly simple, with about 80 percent represented by two amino acids. The team then made an artificial version of the molecule, which they named “multi-tasking protein,” in the lab.
Next the researchers performed a simplified version of the jaw formation process. They added copper to the beakers with their artificial multi-tasking protein and observed that the two materials become concentrated into little droplets. When the researchers added a molecule called Dopa (which other animals often convert into melanin), the droplets turned darker and formed a dense film.
“We noticed that if you put a pin tip into the brownish-black film that formed on the surface you could actually pull fibers out of that film and then test them mechanically,” Waite says. “It turned out that the fibers resemble nylon, and that’s a pretty strong fiber.”
The experiment indicates that a single protein plays multiple vital roles in bloodworm jaw formation: binding to copper, concentrating itself into droplets, converting Dopa to melanin, and ultimately forming a composite material. This is much simpler than what must take place to form industrial composites such as fiberglass or reinforced rubber.
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“What the worm is doing to form its jaws gives us a kind of blueprint for how composite materials can be made more sustainably and less reliant on heavy equipment, for example, mixers, blenders, extruders,” Waite says. “Certainly those don’t exist in the bloodworm system and yet a very organized material is forming.”
The chemical reactions that bloodworms use to make their fangs are very sensitive to the acidity, salinity, and temperature of the surrounding seawater. This could mean that bloodworms are vulnerable to the effects of climate change, Waite says.
Still, the bloodworms’ natural knack of creating tough materials offers a valuable lesson, says Waite. With their remarkable jaw-formation process, Waite sees similarities in some respects to the giant sandworms that populate the Dune novels.
“These worms that lived in a wasteland produced something called spice that everyone in the universe wanted,” Waite says. “It’s been a reminder, in an exaggerated way, that simple organisms can harbor really useful technologies.”